Solid electrolytic capacitor and method of manufacturing the same

ABSTRACT

A solid electrolytic capacitor includes a capacitor element, an anode terminal, and a cathode terminal. The capacitor element has an element body. An outer circumference of the element body is defined by first to fourth side surfaces. An exposed surface of a cathode layer is defined at least on the second and third side surfaces. The cathode terminal has first and second terminal component parts. The first terminal component part extends along the third side surface. The second terminal component part adjoins the first terminal component part while extending above the second side surface. A first conductive adhesive is interposed between the first terminal component part and the third side surface. A second conductive adhesive is interposed between the second terminal component part and the second side surface. The second conductive adhesive extends along the second side surface to reach the peripheral edge of the fourth side surface.

Japanese patent application Number 2010-138009, upon which this patentapplication is based, is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a solid electrolytic capacitor and a method ofmanufacturing the solid electrolytic capacitor.

2. Description of Related Art

A solid electrolytic capacitor includes a capacitor element, an anodeterminal, and a cathode terminal. The capacitor element has an elementbody with an outer circumference the region of which is at leastpartially defined by a cathode layer, and an anode lead pulled out ofthe element body through the outer circumference of the element body.The anode terminal is electrically connected to an anode lead. Thecathode terminal is electrically connected to a cathode layer.

The solid electrolytic capacitor may have the structure as follows. Theelement body is in the form of a rectangular parallelepiped. The outercircumference of the element body is defined by a first side surfacethrough which the anode lead is pulled out, a second side surfaceopposite the first side surface, and third and fourth side surfacesopposite each other and which extend between peripheral edges of thefirst side surface and peripheral edges of the second side surface. Thecathode terminal has first and second terminal component parts. Thefirst terminal component part extends along the third side surface ofthe element body. The second terminal component part adjoins the firstterminal component part, and extends above the second side surface ofthe element body.

In the aforementioned conventional structure of the solid electrolyticcapacitor, the cathode layer forms at least the third side surface ofthe outer circumference of the element body, and a conductive adhesiveis interposed between the third side surface and the first terminalcomponent part. This forms satisfactory electrical connection betweenthe cathode terminal and the cathode layer, allowing the conventionalsolid electrolytic capacitor to achieve ESR (equivalent seriesresistance) required at the time of development of the solidelectrolytic capacitor.

Meanwhile, the solid electrolytic capacitor has been required to achievelower ESR in response to a recent trend toward higher performance of anelectronic device in which the solid electrolytic capacitor is to beincorporated.

SUMMARY OF THE INVENTION

A solid electrolytic capacitor of the invention includes a capacitorelement, an anode terminal, and a cathode terminal. The capacitorelement has an element body with an outer circumference the region ofwhich is at least partially defined by a cathode layer, and an anodelead pulled out of the element body through the outer circumference ofthe element body. The outer circumference of the element body is definedby a first side surface through which the anode lead is pulled out, asecond side surface opposite the first side surface, and third andfourth side surfaces opposite each other and which extend betweenperipheral edges of the first side surface and peripheral edges of thesecond side surface. An exposed surface of the cathode layer is definedat least on the second and third side surfaces of the outercircumference of the element body. The anode terminal is electricallyconnected to the anode lead. The cathode terminal is electricallyconnected to the cathode layer. The cathode terminal has first andsecond terminal component parts. The first terminal component partextends along the third side surface of the element body. The secondterminal component part adjoins the first terminal component part whileextending above the second side surface of the element body. A firstconductive adhesive is interposed between the first terminal componentpart and the third side surface of the element body. A second conductiveadhesive is interposed between the second terminal component part andthe second side surface of the element body. The second conductiveadhesive extends along the second side surface of the element body toreach the peripheral edge of the fourth side surface.

A manufacturing method of the invention is a method of manufacturing asolid electrolytic capacitor. The solid electrolytic capacitor includesa capacitor element, an anode terminal, and a cathode terminal. Thecapacitor element has an element body with an outer circumference theregion of which is at least partially defined by a cathode layer, and ananode lead pulled out of the element body through the outercircumference of the element body. The outer circumference of theelement body is defined by a first side surface through which the anodelead is pulled out, a second side surface opposite the first sidesurface, and third and fourth side surfaces opposite each other andwhich extend between peripheral edges of the first side surface andperipheral edges of the second side surface. An exposed surface of thecathode layer is defined at least on the second and third side surfacesof the outer circumference of the element body. The anode terminal iselectrically connected to the anode lead. The cathode terminal iselectrically connected to the cathode layer. The cathode terminal hasfirst and second terminal component parts. The first terminal componentpart extends along the third side surface of the element body. Thesecond terminal component part adjoins the first terminal component partwhile extending above the second side surface of the element body. Themanufacturing method includes steps (a) and (b). In the step (a), theelement body is placed on a surface of the first terminal component partafter applying the first conductive adhesive to the surface of the firstterminal component part. The element body is placed with the third sidesurface of the element body facing the surface of the first terminalcomponent part such that the first conductive adhesive is interposedbetween the third side surface of the element body and the firstterminal component part. The step (b) is performed after the step (a).In the step (b), a second conductive adhesive is applied to fill spacebetween the second terminal component part and the second side surfaceof the element body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a solid electrolytic capacitor of anembodiment of the invention;

FIG. 2 is a perspective view of an anode frame and a cathode frame tobecome an anode terminal and a cathode terminal respectively of thesolid electrolytic capacitor;

FIG. 3 is a perspective view showing an element placing step of a methodof manufacturing the solid electrolytic capacitor;

FIG. 4 is a side view showing a capacitor element and a conductiveadhesive in a state after the element placing step is performed;

FIG. 5 is a side view showing a filling step of the manufacturingmethod;

FIG. 6 is a side view showing an outer package forming step of themanufacturing method;

FIG. 7 is a side view showing a cutting step of the manufacturingmethod;

FIG. 8 is a side view showing a terminal forming step of themanufacturing method;

FIG. 9 is a perspective view of an anode frame and a cathode frame tobecome an anode terminal and a cathode terminal respectively of a firstmodification of the solid electrolytic capacitor;

FIG. 10 is a top view showing an element placing step of a method ofmanufacturing the solid electrolytic capacitor of the firstmodification;

FIG. 11 is a top view showing a filling step of the method ofmanufacturing the solid electrolytic capacitor of the firstmodification; and

FIG. 12 is a sectional view of a second modification of the solidelectrolytic capacitor.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a perspective view of a solid electrolytic capacitor of anembodiment of the invention. As shown in FIG. 1, the solid electrolyticcapacitor includes a solid electrolytic capacitor element 1, an outerpackage member 2 covering the capacitor element 1, an anode terminal 3,and a cathode terminal 4. In the embodiment, the outer package member 2is made of resin such as an epoxy resin.

The capacitor element 1 has an element body 10 in the form of arectangular parallelepiped, and an anode lead 12 pulled out of theelement body 10 through its outer circumference. The outer circumferenceis defined by a first side surface 101 through which the anode lead 12is pulled out, a second side surface 102 opposite the first side surface101, and third and fourth side surfaces 103 and 104 opposite each otherand which extend between peripheral edges of the first side surface 101and peripheral edges of the second side surface 102.

The element body 10 includes an anode body 11 in the form of arectangular parallelepiped in which the anode lead 12 is implanted, adielectric layer 13 formed on a surface of the anode body 11, anelectrolyte layer 14 formed on the dielectric layer 13, and a cathodelayer 15 formed on the electrolyte layer 14. The anode lead 12 is in theform of a column.

The anode body 11 is constructed of a porous sintered body made of avalve acting metal. Examples of the valve acting metal include tantalum,niobium, titanium, and aluminum. The anode lead 12 has a base endportion 122 buried in the anode body 11, and a tip end portion 121pulled out of the anode body 11 through its surface. The anode lead 12is made of a valve acting metal the type of which is the same as ordifferent from the valve acting metal constituting the anode body 11.The anode body 11 and the anode lead 12 are electrically connected toeach other.

The dielectric layer 13 is constructed of an oxide film formed on thesurface of the anode body 11. The oxide film is formed by dipping theanode body 11 into an electrolytic solution such as a phosphorussolution and an adipic acid solution, and by electrochemically oxidizingthe surface of the anode body 11 (anodic oxidation).

The electrolyte layer 14 is made of an electrolyte material that can besolidified on the dielectric layer 13. the electrolyte material may be aconductive inorganic material such as manganese dioxide, or a conductiveorganic material such as TCNQ (tetracyanoquinodimethane) complex saltand conductive polymer. The cathode layer 15 is constructed of a carbonlayer (not shown) formed on the electrolyte layer 14, and a silver paintlayer (not shown) formed on the carbon layer. The electrolyte layer 14and the cathode layer 15 are electrically connected to each other. Thecathode layer 15 forms at least the second and third side surfaces 102and 103 of the outer circumference of the element body 10. So, anexposed surface of the cathode layer 15 is defined on the second andthird side surfaces 102 and 103. In the embodiment, the cathode layer 15also forms the fourth side surface 104.

In the capacitor element 1, part of the anode lead 12 pulled out of theanode body 11 and the cathode layer 15 form anode and cathode parts ofthe capacitor element 1 respectively, and the dielectric layer 13 andthe electrolyte layer 14 are placed between the anode and cathode parts.

The anode terminal 3 is electrically connected to the anode lead 12, andpart of the anode terminal 3 is exposed to the outer circumference ofthe outer package member 2. The cathode terminal 4 is electricallyconnected to the cathode layer 15, and part of the cathode terminal 4 isexposed to the outer circumference of the outer package member 2.

More specifically, the anode lead 12 and the anode terminal 3 areelectrically connected to each other by welding. The anode terminal 3 ispulled out to a first side surface 201 forming the outer circumferenceof the outer package member 2, and which is defined forward of the tipend of the anode lead 12. The anode terminal 3 extends downward alongthe first side surface 201, and then bends at a lower edge 201 a of thefirst side surface 201, thereby defining a tip end portion 30 of theanode terminal 3 along a lower surface 203 of the outer package member2.

The cathode terminal 4 has first and second terminal component parts 41and 42. The first terminal component part 41 extends along the thirdside surface 103 of the element body 10. The second terminal componentpart 42 adjoins the first terminal component part 41, and extends abovethe second side surface 102 of the element body 10. In the embodiment,the second terminal component part 42 extends diagonally downward leftfrom the left edge of the first terminal component part 41 as shown inFIG. 1. The cathode terminal 4 further has a third terminal componentpart 43 that adjoins the lower edge of the second terminal componentpart 42. The third terminal component part 43 extends in a directionsubstantially parallel to the lower surface 203 of the outer packagemember 2 to reach a second side surface 202 of the outer package member2 opposite the first side surface 201.

A first conductive adhesive 51 is interposed between the first terminalcomponent part 41 and the third side surface 103 of the element body 10.A second conductive adhesive 52 is interposed between the secondterminal component part 42 and the second side surface 102 of theelement body 10. The second conductive adhesive 52 extends along thesecond side surface 102 to reach the lower edge of the second sidesurface 102 (in FIG. 1, the left edge of the fourth side surface 104).As a result, electrical connection is made between the cathode layer 15and the cathode terminal 4. The type of the second conductive adhesive52 may be the same as or different from that of the first conductiveadhesive 51.

The cathode terminal 4 is pulled out to the second side surface 202 ofthe outer package member 2. The cathode terminal 4 extends downwardalong the second side surface 202, and then bends at a lower edge 202 aof the second side surface 202, thereby defining a tip end portion 40 ofthe cathode terminal 4 along the lower surface 203 of the outer packagemember 2.

A method of manufacturing the solid electrolytic capacitor of theembodiment is described in detail next by referring to drawings. Themanufacturing method includes an element placing step, a filling step,an outer package forming step, a cutting step, and a terminal formingstep performed in this order.

First, an anode frame 61 to become the anode terminal 3 and a cathodeframe 62 to become the cathode terminal 4 are prepared as shown in FIG.2 before the element placing step starts. The cathode frame 62 is bentto define the first and second terminal component parts 41 and 42.

FIG. 3 is a perspective view showing the element placing step. In theelement placing step, the first conductive adhesive 51 is applied to asurface of the first terminal component part 41, and thereafter thecapacitor element 1 is placed on the anode and cathode frames 61 and 62as shown in FIG. 3. More specifically, the element body 10 is placed onthe surface of the first terminal component part 41 with the third sidesurface 103 facing the surface of the first terminal component part 41.As a result, the first conductive adhesive 51 extends over the surfaceof the first terminal component part 41 as shown in FIG. 4, so that thefirst conductive adhesive 51 is extensively interposed between the thirdside surface 103 and the first terminal component part 41. This formssatisfactory electrical connection between the first terminal componentpart 41 and the cathode layer 15.

In the element placing step, the tip end portion 121 of the anode lead12 is made to contact the anode frame 61, and contact surfaces of theanode lead 12 and the anode frame 61 are subjected to welding, therebyforming satisfactory electrical connection between the anode lead 12 andthe anode frame 61.

FIG. 5 is a side view showing the filling step. In the filling step, thesecond conductive adhesive 52 is applied to fill space between thesecond terminal component part 42 and the second side surface 102 of theelement body 10 as shown in FIG. 5. To be specific, the secondconductive adhesive 52 is applied such that it extends along the secondside surface 102 to reach the left edge of the fourth side surface 104as shown in FIG. 5. Thus, the second conductive adhesive 52 isinterposed between the second side surface 102 and the second terminalcomponent part 42, while the second conductive adhesive 52 extensivelycontacts the second side surface 102. This forms satisfactory electricalconnection between the second terminal component part 42 and the cathodelayer 15. The type of the second conductive adhesive 52 may be the sameas or different from that of the first conductive adhesive 51.

FIG. 6 is a side view showing the outer package forming step. In theouter package forming step, the capacitor element 1 is covered by resinsuch as an epoxy resin by using a molding technique as shown in FIG. 6.As a result, the outer package member 2 is formed, and the capacitorelement 1 is covered by the outer package member 2.

FIG. 7 is a side view showing the cutting step. In the cutting step, asshown in FIG. 7, the anode frame 61 is cut along a line A-A shown inFIG. 6 such that a length L1 of the anode frame 61 from the first sidesurface 201 of the outer package member 2 becomes a given length.Further, the cathode frame 62 is cut along a line B-B shown in FIG. 6such that a length L2 of the cathode frame 62 from the second sidesurface 202 of the outer package member 2 becomes a given length.

FIG. 8 is a side view showing the terminal forming step. In the terminalforming step, as shown in FIG. 8, part of the anode frame 61 pulled outto the first side surface 201 is bent, and the bent part is made toextend along the first side surface 201 and along a surface of the outerpackage member 2 to become the lower surface 203 (see FIG. 1). Then, theanode frame 61 becomes the anode terminal 3, and the tip end portion 30of the anode terminal 3 is defined along the surface of the outerpackage member 2 to become the lower surface 203.

In the terminal forming step, part of the cathode frame 62 pulled out tothe second side surface 202 is also bent, and the bent part is made toextend along the second side surface 202 and the surface to become thelower surface 203. Then, the cathode frame 62 becomes the cathodeterminal 4, and the tip end portion 40 of the cathode terminal 4 isdefined along the surface to become the lower surface 203.

In the solid electrolytic capacitor, the cathode layer 15 forms thesecond and third side surfaces 102 and 103 of the element body 10.Further, the conductive adhesives 51 and 52 contact not only the thirdside surface 103, but they also extensively contact the second sidesurface 102. This makes area in which the cathode terminal 4 and thecathode layer 15 are electrically connected greater than that of aconventional solid electrolytic capacitor in which a conductive adhesiveis interposed only between the first terminal component part 41 and thethird side surface 103, allowing the solid electrolytic capacitor of theembodiment to achieve lower ESR.

FIG. 9 is a perspective view of a first modification of the solidelectrolytic capacitor, and which shows the anode frame 61 and thecathode frame 62 to become the anode terminal 3 and the cathode terminal4 respectively of the solid electrolytic capacitor of the firstembodiment. As shown in FIG. 9, the second terminal component part 42 ofthe cathode frame 62 may be provided with an opening 44 that passesthrough the second terminal component part 42 from its front surface toits rear surface. In the first modification, the opening 44 may bedefined not only the second terminal component part 42 but also in aregion 621 of the cathode frame 62 to become the third terminalcomponent part 43 of the cathode terminal 4.

In order to form the solid electrolytic capacitor of the firstmodification, as shown in FIG. 10 (and by referring to FIG. 4), thecapacitor element 1 is placed on the anode and cathode frames 61 and 62in the element placing step. Next, in the filling step, the secondconductive adhesive 52 is applied to fill space between the secondterminal component part 42 and the second side surface 102 of theelement body 10 such that the opening 44 is not filled with the secondconductive adhesive 52 as shown in FIG. 11. So, in the solidelectrolytic capacitor as formed, the second conductive adhesive 52 isinterposed between the second terminal component part 42 and the secondside surface 102, and the opening 44 remains exposed without beingfilled with the second conductive adhesive 52.

In the solid electrolytic capacitor of the first modification, resindefined on the front surface of the second terminal component part 42and resin defined on the rear surface of the second terminal componentpart 42 that are part of the outer package member 2 are connected toeach other through the opening 44 defined in the second terminalcomponent part 42. This enhances the strength of the outer packagemember 2 at a place near the second terminal component part 42, so thata defect such as a crack is unlikely to occur in the outer packagemember 2 even if stress is generated in the outer package member 2 as aresult of bending of the cathode terminal 4 in the terminal forming step(see FIG. 8).

FIG. 12 is a sectional view of a second modification of the solidelectrolytic capacitor. As shown in FIG. 12. in the solid electrolyticcapacitor of the second modification, the cathode layer 15 may form thefourth side surface 104 as well as the second and third side surfaces102 and 103 of the element body 10, and part of the second conductiveadhesive 52 may extend further to cover the fourth side surface 104 ofthe element body 10. This further increases a contact area between thecathode terminal 4 and the cathode layer 15 of the capacitor element 1,resulting in further reduction of ESR.

The structure of each part of the invention is not limited to that shownin the embodiment described above. Various modifications can be devisedwithout departing from the technical scope recited in claims. By way ofexample, in the solid electrolytic capacitor shown in FIG. 1, the secondterminal component part 42 may extend in a direction substantiallyvertical to the first terminal component part 41. Namely, the secondterminal component part 42 may extend in a direction substantiallyparallel to the second side surface 102 of the element body 10.

The structures of the capacitor element 1, the outer package member 2,the anode terminal 3, the cathode terminal 4, and the conductiveadhesives 51 and 52 are not limited to those shown in the embodimentdescribed above. Various modifications thereof can be devised withoutdeparting from the technical scope recited in claims.

1. A solid electrolytic capacitor, comprising: a capacitor elementhaving an element body with an outer circumference the region of whichis at least partially defined by a cathode layer, and an anode leadpulled out of the element body through the outer circumference of theelement body; an anode terminal electrically connected to the anodelead; and a cathode terminal electrically connected to the cathodelayer, wherein the outer circumference of the element body is defined bya first side surface through which the anode lead is pulled out, asecond side surface opposite the first side surface, and third andfourth side surfaces opposite each other and which extend betweenperipheral edges of the first side surface and peripheral edges of thesecond side surface, and an exposed surface of the cathode layer isdefined at least on the second and third side surfaces of the outercircumference of the element body, and the cathode terminal has a firstterminal component part extending along the third side surface of theelement body, and a second terminal component part adjoining the firstterminal component part while extending above the second side surface ofthe element body, a first conductive adhesive is interposed between thefirst terminal component part and the third side surface of the elementbody, a second conductive adhesive is interposed between the secondterminal component part and the second side surface of the element body,and the second conductive adhesive extends along the second side surfaceof the element body to reach the peripheral edge of the fourth sidesurface.
 2. The solid electrolytic capacitor according to claim 1,wherein the second terminal component part is provided with an openingthat passes through the second terminal component part from its frontsurface to its rear surface, and the second conductive adhesive isinterposed between the second terminal component part and the secondside surface of the element body while the opening is not filled withthe second conductive adhesive.
 3. A method of manufacturing a solidelectrolytic capacitor, the solid electrolytic capacitor comprising: acapacitor element having an element body with an outer circumference theregion of which is at least partially defined by a cathode layer, and ananode lead pulled out of the element body through the outercircumference of the element body; an anode terminal electricallyconnected to the anode lead; and a cathode terminal electricallyconnected to the cathode layer, the outer circumference of the elementbody being defined by a first side surface through which the anode leadis pulled out, a second side surface opposite the first side surface,and third and fourth side surfaces opposite each other and which extendbetween peripheral edges of the first side surface and peripheral edgesof the second side surface, an exposed surface of the cathode layerbeing defined at least on the second and third side surfaces of theouter circumference of the element body, the cathode terminal having afirst terminal component part extending along the third side surface ofthe element body, and a second terminal component part adjoining thefirst terminal component part while extending above the second sidesurface of the element body, the method comprising the steps of: (a)placing the element body on a surface of the first terminal componentpart after applying the first conductive adhesive to the surface of thefirst terminal component part, the element body being placed with thethird side surface of the element body facing the surface of the firstterminal component part such that the first conductive adhesive isinterposed between the third side surface of the element body and thefirst terminal component part; and (b) applying a second conductiveadhesive to fill space between the second terminal component part andthe second side surface of the element body after the step (a).
 4. Themethod according to claim 3, wherein application of the secondconductive adhesive in the step (b) is such that the second conductiveadhesive extends along the second side surface of the element body toreach the peripheral edge of the fourth side surface of the elementbody.
 5. The method according to claim 3, wherein the second terminalcomponent part is provided with an opening that passes through thesecond terminal component part from its front surface to its rearsurface, and application of the second conductive adhesive to fill thespace between the second terminal component part and the second sidesurface of the element body in the step (b) is such that the opening isnot filled with the second conductive adhesive.